RU2541775C2 - Method for identifying microorganisms from test blood culture sample - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention aims at a method for identifying microorganisms from a test blood culture sample. The method provides preparing a test sample, conducting a selective lysis and dissolving the cells other than microorganisms of the test sample, laminating the prepared lysate on a density buffer in a hermetically sealed container and centrifuging. The density buffer has a uniform density from approximately 1.025 g/ml to approximately 1.120 g/ml. The microorganisms passing through the above buffer are precipitated on a container bottom. The precipitate is analysed with the use of Raman spectroscopy that enables identifying a genus or a species of the microorganism.

EFFECT: invention enables identifying the microorganisms from the clinical samples over less than 120 min.

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Description

CROSS REFERENCE TO A RELATED APPLICATION

This application claims priority with respect to provisional patent application US No. 61/110187, entitled "Method and System for Detection and / or Characterization of a Biological Particle in a Sample", filed October 31, 2008, which is included in this application.

FIELD OF THE INVENTION

The present invention relates to methods and systems for detecting, isolating and / or identifying microorganisms in a sample. In particular, the present invention is a direct method for the rapid characterization and / or identification of a microorganism using Raman spectroscopic methods.

BACKGROUND OF THE INVENTION

Detection of pathogenic microorganisms in biological fluids should be carried out as soon as possible, in particular in the case of septicemia, for which mortality remains high, despite the wide range of antibiotics available to doctors. The presence of biologically active agents, such as microorganisms, in the patient’s body fluid, in particular in the blood, is usually determined using blood culture vials. Infections of the circulatory system are associated with high morbidity and mortality, in addition, the implementation of modern methods of diagnosis, cultivation, followed by biochemical identification and testing for sensitivity to antibiotics can take several days. Empirical therapy is usually started on the basis of clinical symptoms, and test results affect clinical decisions only when the initial therapy is unsuccessful. The ability to characterize circulatory infections within the first few hours, preferably within an hour, after a positive blood culture result would significantly enhance the clinical relevance of the diagnostic information provided. Molecular amplification methods have been proposed to meet this need, but serious problems remain with this approach. The positive blood culture medium itself is a naturally amplified population of microorganisms with the potential to use rapid identification tests (IDs).

Conventional automatic phenotypic ID tests, such as Vitek®, Phoenix ™ and Microscan® systems, or manual phenotypic tests, such as APIs, require microorganisms to be in the appropriate growth phase and free from interfering media and blood products in order to obtain reliable results. . These systems use colonies grown from a positive culture for 18-24 hours on media in Petri dishes. However, in an effort to obtain faster results, some laboratories reported the use of these systems with microorganisms isolated from vials with positive blood cultures. These tests "directly from the bottle" are not suitable for all microorganisms (for example, not suitable for gram-positive cocci), are not confirmed by the manufacturers of the tests and, as a rule, take 3-8 hours to obtain results. Faster and more widely specific tests are essential in order to provide the clinician with clinically relevant results within the first few hours, preferably within an hour, after a positive culture result.

Raman spectroscopy has the potential to identify microorganisms very quickly, but may encounter interference from a variety of highly fluorescent and absorbing compounds present in liquid microbiological culture media and in clinical samples such as blood, or in combination. The most commonly used methods for isolating microorganisms directly from positive blood culture are two-stage differential centrifugation and centrifugation in vitro to separate serum.

Other described methods for the separation, characterization and / or identification of microorganisms include:

US Pat. No. 4,847,198 discloses a method for identifying microorganisms using Raman spectroscopy with UV excitation. According to the '198 patent, a bacterial suspension is brought into contact with a single wavelength in the ultraviolet range. Part of the used light energy is absorbed, and part of the light energy is emitted. The emitted light energy amplified by the resonance Raman light scattering is measured as backscattered energy. This energy is processed to obtain spectra that are characteristic of bacteria.

US Pat. No. 5,938,617 to Vo-Dinh is directed to a system that identifies biological pathogens in a sample by exciting the sample with light at multiple wavelengths and simultaneously removing emission intensities. This system includes mechanisms for exposing the sample to exciting radiation and for the resultant generation of emitted radiation. Biological pathogens can be viruses and bacteria.

US Pat. No. 6,177,266 discloses a method for chemotaxonomic classification of bacteria by biomarkers specific to the genus, species, and strain created by mass spectrometry analysis of time-of-flight ionization by laser desorption using a matrix (MALDI-TOF-MS) or cellular protein extracts or whole cells.

US patent No. 7070739 provides a method for the extraction, separation and purification of microorganisms, including viruses, by two-dimensional ultracentrifugation directly from body fluids or from homogenized tissue. In the first centrifugation step, all particles having a higher sedimentation rate than those of the microorganisms that need to be identified are removed. At the second stage of ultracentrifugation, zonal centrifugation in a density gradient in liquids filled with the formation of a wide range density gradient using special corrugated centrifuge tubes is used. In accordance with this patent, this separation method can be used to determine grouped particles by light scattering or fluorescence using nucleic acid-specific dyes and to isolate grouped particles in very small volumes for characterization by mass spectrometry of viral protein and intact viral subunits particles, as well as using fluorescence flow cytometric determination of both the mass of nucleic acids and the masses of fragments formed by restriction enzymes .

US Published Patent Application No. 2007/0037135 discloses a system for identifying and quantifying a biological sample suspended in a liquid. This system includes a fluorescence excitation module with at least one exciting light source; a sample interface module optically coupled to a fluorescence excitation module for arranging the biological sample so that it receives exciting light from at least one exciting light source; a fluorescence emission module optically coupled to a sample interface module and including at least one detection device for detecting fluorescence excitation-emission matrices of a biological sample; and a computer module operatively connected to the fluorescence emission module. The computer module performs multivariate analysis on the fluorescence excitation-emission matrices of a biological sample in order to identify and quantify the biological sample. However, the '135 application does not discuss the identification and quantification of microorganisms from complex biological samples such as blood.

US Patent Application Publication No. 2007/0175278 describes the use of a liquid culture medium for culturing a sample of interest, including, for example, blood, urine, feces, intravenous catheters, etc., industrial production lines, water systems, food product, cosmetic product , pharmaceutical product and forensic sample. Therefore, microorganisms can be collected from a liquid medium by methods known in the art, for example by centrifugation. Concentrated microorganisms can then be transferred onto a carrier material, optionally after drying, to obtain a vibrational spectrum. The patent application discusses various methods for identifying and classifying microorganisms, including vibration spectroscopy, such as Raman spectroscopy.

However, these methods have several drawbacks when trying to separate and characterize microorganisms from complex samples, such as culture media containing blood. The resulting microorganism preparations often contain contaminating red blood cells, platelets, lipid particles, plasma enzymes and cell detritus, which can cause poor results. These methods are also very time-consuming and unsafe due to the steps that can result in aerosol exposure of potentially dangerous pathogens to the user. Simple, safe, and reliable methods of isolating microorganisms from clinical samples (e.g., blood culture) and other complex samples that are free of these interfering materials and compatible with rapid identification technologies are needed.

SUMMARY OF THE INVENTION

The present invention provides methods for the separation, characterization and / or identification of microorganisms in a sample. These methods enable the characterization and / or identification of microorganisms faster than the methods of the prior art, resulting in faster diagnoses (for example, in a subject suffering or suspected of septicemia) and the identification of infected materials (for example, food products and pharmaceuticals) . The steps included in the methods of the invention, from obtaining a sample for characterization and / or identification of microorganisms to obtaining clinically relevant information giving rise to action, can be carried out in a very short time frame, for example in less than about 120 minutes. In addition, the methods of the invention can be fully automated, thereby reducing the risk of handling infectious materials and / or infected samples.

In one aspect, the present invention is directed to a method for characterizing and / or identifying a microorganism from a test sample, comprising:

(a) obtaining a test sample that is known to contain or may contain microorganisms;

(b) selective lysis of non-microorganism cells in the test sample to obtain a lysed sample;

(c) separating microorganisms from other components of the lysed sample to form an isolated sample of microorganisms;

(d) the study of isolated microorganisms using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of the microorganism; and

(e) characterization and / or identification of a given microorganism in an isolated sample by comparing spectroscopic measurements with spectroscopic measurements or the predicted spectroscopic properties of known microorganisms.

In one aspect, the present invention is directed to a method for characterizing and / or identifying a microorganism from a blood culture, including:

(a) obtaining a sample from a blood culture that is known to contain or may contain microorganisms;

(b) selective lysis of non-microorganism cells in the sample to produce a lysed sample;

(c) layering the lysed sample on a density buffer in an airtight container;

(d) centrifuging a container to separate microorganisms from other components of the sample and precipitate microorganisms;

(e) spectroscopic study of isolated microorganisms in situ using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of the microorganism; and

(f) characterization and / or identification of a given microorganism in an isolated sample by comparing spectroscopic measurements with spectroscopic measurements taken or the predicted spectroscopic properties of known microorganisms.

In another aspect, the present invention is directed to a method for characterizing and / or identifying a microorganism, including:

(a) obtaining a test sample that is known to contain or may contain microorganisms;

(b) placing the test sample in a sealed container;

(c) in situ separation of microorganisms from other components of the test sample to form an isolated microorganism sample from the microorganisms in an airtight container;

(d) in situ spectroscopic investigation of isolated microorganisms using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of the microorganism; and

(e) characterization and / or identification of a given microorganism in an isolated sample by comparing spectroscopic measurements with spectroscopic measurements or the predicted spectroscopic properties of known microorganisms.

In one embodiment, separation is effected by layering the test sample on a density buffer in an airtight container (e.g., a hermetically sealed container) and centrifuging the container to deposit microorganisms, while the medium of the test sample remains on top of the density buffer. In another embodiment, the container has an optical window at the bottom and / or on the walls, so that the sediment of microorganisms can be examined spectroscopically. Microorganisms can be identified by comparing the spectrum of the precipitate with the spectrum or spectra or the predicted spectroscopic properties of known microorganisms. The ability to identify microorganisms directly in the sediment without additional manipulation significantly improves the safety of identification of microorganisms.

In one embodiment, spectroscopy is based on the vibrational structure of constituent molecules that contain microorganisms. In other forms of implementation, spectroscopic examination is based in part on signals obtained from additional agents that are added in the process of the methods of the invention and which interact with specific microorganisms or groups of microorganisms.

In another embodiment, the methods further include the step of isolating the microorganism sediment, resuspending the microorganism, and conducting additional identification or characterization tests (e.g., drug resistance, virulence factors, antibiograms).

The present invention is explained in more detail in the graphic materials of this application and in the description below.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

In FIG. 1 shows the Raman spectra of various microorganisms treated and isolated from blood culture.

In FIG. Figure 2 shows the Raman spectra of 13 S. aureus isolates isolated directly from the culture medium of the blood culture.

In FIG. Figure 3 shows Raman spectra taken through a sealed separator in the presence and absence of microorganisms.

In FIG. 4 shows the Raman spectra of the sediment of a microorganism isolated from blood culture, taken through an airtight separator, the background is subtracted.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be implemented in various forms and should not be construed as limited by the forms of implementation set forth in this application. Most likely, these forms of implementation are presented so that this description is more thorough and complete and fully conveys the scope of the invention to specialists in this field of technology. For example, features illustrated in relation to one implementation form may be included in other forms of implementation, and features illustrated in relation to a specific implementation form may be removed from this implementation form. In addition, various changes and additions to the forms of implementation proposed here, which do not deviate from the present invention, will be apparent to those skilled in the art in light of the present description.

Unless otherwise specified, all technical and scientific terms used in this application have the same meaning that is generally understood by ordinary experts in the field of technology to which this invention belongs. The terminology used in the description of the invention in this application is intended only for the purpose of describing specific forms of implementation and is not intended to limit the invention.

Definitions

As used in this application, the singular may mean one or more than one. For example, “cell” may mean a single cell or multiple cells.

As used in this application, "and / or" also refers to any or all possible combinations of one or more of one of the related items listed and includes them, as well as the lack of combinations when interpreted in an alternative ("or").

In addition, the term "about" as used in this application in relation to a measurable value, such as the amount of a compound or agent of this invention, dose, time, temperature and the like, is meant as encompassing variations of ± 20%, ± 10%, ± 5%, ± 1%, ± 0.5%, or even ± 0.1% of the specified amount.

As used in this application, the term "microorganism" is intended to include organisms that are generally unicellular, which can be propagated and kept in laboratories, including, but not limited to, gram-positive or gram-negative bacteria, yeast, molds, parasites and mollusks. Non-limiting examples of gram-negative bacteria of the present invention include bacteria of the following genera: Pseudomonas, Escherichia, Salmonella, Shigella, Enterobacter, Klebsiella, Serratia, Proteus, Campylobacter, Haemophilus, Morganella, Vibrio, Yersinia, Acinetobacter, Arenovromasbromonium, Acinetobacteron, Breenbromonium , Prevotella, Branhamella, Neisseria, Burkholderia, Citrobacter, Hafhia, Edwardsiella, Aeromonas, Moraxella, Brucella, Pasteurella, Providencia and Legionella. Non-limiting examples of gram-positive bacteria of the invention include bacteria of the following genera: Enterococcus, Streptococcus, Staphylococcus, Bacillus, Paenibacillus, Lactobacillus, Listeria, Peptostreptococcus, Propionibacterium, Clostridium, Bacteroides, Gardnerella, Lococococio, Micrococococia, Micrococococcus, Leococococcus, Microcococcus, Microcococcus, Microcococcus, Micrococococcus, Leococococi, Microcococcus, Microcococcus, Microcococcus, Microcococcus, Microcococcus, Microcococcus, Micrococcus, Micrococcus, and Micrococcus. Non-limiting examples of yeast and molds of the present invention include yeast and molds from the following genera: Candida, Cryptococcus, Nocardia, Penicillium, Alternaria, Rhodotorula, Aspergillus, Fusarium, Saccharomyces and Trichosporon. Non-limiting examples of parasites of this invention include parasites from the following genera: Trypanosoma, Babesia, Leishmania, Plasmodium, Wucheria, Brugia, Onchocerca and Naegleria. Non-limiting examples of the mollicuts of this invention include those of the following genera: Mycoplasma and Ureaplasma.

In one embodiment, as described in more detail herein, microorganisms from a sample or from a growth medium can be separated and examined to characterize and / or identify the microorganism present in the sample. As used in this application, the term “split” is meant to include any sample of microorganisms that are recovered, concentrated, or otherwise removed from its original state or from a growth or culture medium. For example, in accordance with this invention, microorganisms can be separated (for example, in the form of an isolated sample) from non-microorganisms or components of non-microorganisms that might otherwise interfere with characterization and / or identification. This term may include a layer of microorganisms laid between two other layers, for example, microorganisms collected on top of a high density density buffer after centrifugation, or a layer of microorganisms collected on a solid surface (for example, on a filter membrane). The term may also include a collection of microorganisms that has partially passed through a layer (e.g., density buffer). As such, an isolated sample of microorganisms can include any collection or layer of microorganisms and / or their components that are more concentrated or otherwise separated from the original sample, and can range from a closely packed dense lump of microorganisms to a diffuse layer of microorganisms. Components of microorganisms that may be contained in isolated form or in a sample include, without limitation, drank, flagella, fimbriae and capsules in any combination. Components of non-microorganisms that are separated from microorganisms may include cells of non-microorganisms (e.g., blood cells and / or cells of another tissue) and / or any components thereof.

In yet another embodiment, as described in more detail herein, microorganisms from a sample or from a growth medium can be isolated and examined to characterize and / or identify the microorganism present in the sample. As used in this application, the term "isolated" is intended to include any sample of microorganisms that is at least partially purified from its original state or from a growth or culture medium and any non-microorganisms or components of non-microorganisms contained therein. For example, in accordance with this invention, microorganisms can be isolated (for example, in the form of an isolated sample) from non-microorganisms or components of non-microorganisms that might otherwise interfere with characterization and / or identification. Components of non-microorganisms that are separated from microorganisms may include cells of non-microorganisms (e.g., blood cells and / or cells of another tissue) and / or any components thereof.

In yet another embodiment, as described in more detail herein, microorganisms from a sample or from a growth medium can be precipitated and examined to characterize and / or identify the microorganism present in the sample. As used in this application, the term "sediment" is intended to include any sample of microorganisms that are compressed or deposited in the mass of microorganisms. For example, microorganisms from a sample can be compressed or deposited in bulk at the bottom of the tube by centrifugation or other methods known in the art. This term includes a collection of microorganisms (and / or their components) on the bottom and / or walls of the container after centrifugation. Components of microorganisms that may be contained in the sediment include, without limitation, drank, flagella, fimbriae and capsules in any combination. In accordance with this invention, microorganisms can be precipitated (for example, in the form of a substantially purified precipitate of microorganisms) from non-microorganisms or components of non-microorganisms that might otherwise interfere with characterization and / or identification. Components of non-microorganisms that are separated from microorganisms may include cells of non-microorganisms (e.g., blood cells and / or cells of another tissue) and / or any components thereof.

As used in this application, the term "density buffer" refers to a solution having a uniform density throughout the solution.

The present invention provides methods for isolating, characterizing and / or identifying microorganisms in a sample. In addition, this method may be particularly useful for the separation, characterization and / or identification of microorganisms from complex samples, such as a culture medium containing blood. Fast methods also provide an opportunity for characterization and / or identification of microorganisms faster than the methods of the prior art, resulting in faster diagnoses (for example, in a subject suffering or suspected of septicemia) and characterization / identification of infected materials (for example, food products and pharmaceuticals). The steps involved in the methods of the invention, from obtaining a sample to characterization / identification of microorganisms, can be carried out in a very short time frame to obtain clinically relevant information that provides the basis for action. In some embodiments, the methods of the invention can be completed in less than about 120 minutes, for example, in less than about 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 5, 4, 3 2 or 1 minute. The sheer speed of the methods of the invention represents an improvement over prior art methods. These methods can be used to characterize and / or identify any microorganism, as described in this application. In one embodiment, the microorganism is a bacterium. In another embodiment, the microorganism is yeast. In another form of implementation, the microorganism is a mold. In a further embodiment, the microorganism is a parasite. In another embodiment, the microorganism is a mollicut. In addition, the methods of the invention can be fully automated, thereby reducing the risk of handling infectious materials and / or infection of samples.

In one aspect, the present invention is directed to a method for characterizing and / or identifying a microorganism from a test sample, comprising:

(a) obtaining a test sample known as containing, or which may contain microorganisms;

(b) selective lysis of non-microorganism cells in the test sample to obtain a lysed sample;

(c) separation of microorganisms from other components of the test sample to form an isolated sample of microorganisms;

(d) the study of isolated microorganisms using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of the microorganism; and

(e) characterization and / or identification of a given microorganism in an isolated sample by comparing spectroscopic measurements with spectroscopic measurements or the predicted spectroscopic properties of known microorganisms.

In another aspect, the present invention is directed to a method for characterizing and / or identifying a microorganism, including:

(a) obtaining a test sample known as containing, or which may contain microorganisms;

(b) placing the test sample in a sealed container;

(c) in situ separation of microorganisms from other components of the test sample to form an isolated microorganism sample from the microorganisms in an airtight container;

(d) in situ spectroscopic investigation of isolated microorganisms using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of the microorganism; and

(e) characterization and / or identification of a given microorganism in an isolated sample by comparing spectroscopic measurements with spectroscopic measurements or the predicted spectroscopic properties of known microorganisms.

In another embodiment of the invention, the methods include recovering a precipitate of microorganisms formed during the separation step, or part thereof, from the separation container before the microorganisms are examined. For example, after the formation of a precipitate, the liquid can be sucked off from the precipitate, and the sediment resuspended in a suitable medium (for example, in an environment in which microorganisms are viable). Resuspended microorganisms can be removed from the separation container. Microorganisms can then be examined for characterization and / or identification, for example, in suspension or after they are reprecipitated. In other embodiments, resuspended microorganisms can be examined in a separation container, for example, in suspension or after they are reprecipitated. In the following embodiment, microorganisms isolated from the precipitate can be used directly for further research (for example, Raman spectroscopy, mass spectroscopy) without resuspension.

Samples

Samples that can be tested (i.e., a test sample) by the methods of the invention include both clinical and non-clinical samples in which the presence and / or growth of the microorganism exists or can be suspected, as well as samples of materials that are usually or occasionally tested for the presence of microorganisms. The amount of sample used can vary significantly depending on the versatility and / or sensitivity of the method. Obtaining a sample can be carried out using any set of techniques known to specialists in this field of technology, although one of the advantages of the present invention is that complex types of samples, such as, for example, blood, body fluids and / or other opaque substances, can be tested directly using a little processing system or without extensive processing. In one embodiment, a sample is taken from a culture. In another embodiment, a sample is taken from a microbiological culture (e.g., blood culture). In another embodiment, the sample is suspected of having microorganisms in it, or it is known.

Clinical samples that can be tested include any type of sample typically tested in clinical or research laboratories, including, but not limited to, blood, serum, plasma, blood fractions, articular fluid, urine, seminal fluid, saliva, feces, cerebrospinal fluid , stomach contents, vaginal secretions, tissue homogenates, bone marrow punctures, bone homogenates, sputum, punctures, smears and washings of smears, other body fluids and the like. In another embodiment, a clinical sample can be cultured and a culture sample can be used.

The present invention finds application both in research and in veterinary and medical applications. Suitable subjects from which clinical specimens can be obtained are typically mammalian subjects, but can be any animal. The term "mammal", as used herein, includes, but is not limited to, humans, non-human primates, cattle, sheep, goats, pigs, horses, cats, dogs, rabbits, rodents (eg, rats or mice) etc. Human subjects include infants, children, adolescents, adults, and the elderly. Subjects from which samples can be obtained include, without limitation, mammals, birds, reptiles, amphibians, and fish.

Non-clinical samples that can be tested also include substances covering, but not limited to, food products, beverages, pharmaceuticals, cosmetics, water (e.g. drinking water, non-drinking water and wastewater), seawater ballasts, air, soil, domestic sewage, plant material (e.g. seeds, leaves, stems, roots, flowers, fruits), blood products (e.g. platelets, serum, plasma, white blood cell fractions, etc.), samples of donor organs or tissues, samples biological weapons and so on obnoe. The method is also particularly well suited for real-time testing to monitor infection levels, process control, quality control and the like under industrial conditions. In another embodiment, a non-clinical sample can be cultured and a culture sample can be used.

In one embodiment, samples are obtained from a subject (eg, a patient) suffering from or suspected to be infected with microorganisms. In one embodiment, the subject suffers or suspects septicemia, such as bacteremia or fungemia. The sample may be a blood sample directly from the subject. A sample can be taken from a blood culture grown from a patient’s blood sample, for example, a BacT / ALERT® blood culture. A blood culture sample can be taken from a positive blood culture, for example, a blood culture that shows the presence of a microorganism. In some embodiments, a sample is taken from a positive blood culture within a short time after it is positive, for example within about 6 hours, for example within about 5, 4, 3 or 2 hours, or within about 60 minutes, for example about 55 , 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 4, 3, 2, or 1 minute. In one embodiment, a sample is taken from a culture in which microorganisms are in the log phase of growth. In another embodiment, a sample is taken from a culture in which microorganisms are in a stationary phase.

The present invention provides high sensitivity for the detection, characterization and / or identification of microorganisms. This makes it possible to detect, characterize and / or identify without the initial need to go through the stages of isolation of microorganisms by growing them on a solid or semi-solid medium and selecting grown colonies. Thus, in one embodiment, the sample is not a sample from a colony of a microorganism (e.g., bacteria, yeast, or mold) grown on a solid or semi-solid surface.

The volume of the sample must be large enough to obtain an isolated sample of microorganisms or sediment of microorganisms, which can be investigated after the stage of separation / isolation of the methods according to the invention. The appropriate volumes will depend on the source of the sample and the estimated level of microorganisms in the sample. For example, a positive blood culture will contain a higher level of microorganisms per volume than a sample of drinking water to be tested for infection, so a smaller volume of blood culture may be necessary compared to a sample of drinking water. Typically, the sample size may be less than about 50 ml, for example, less than about 40, 30, 20, 15, 10, 5, 4, 3, or 2 ml. In some embodiments, the sample size may be about 1 ml, for example, about 0.75, 0.5, or 0.25 ml. In some forms of implementation in which the separation is carried out on a micro scale, the sample size may be less than about 200 μl, for example less than about 150, 100, 50, 25, 20, 15, 10, or 5 μl. In some forms of implementation (for example, when it is expected that the sample contains a small number of microorganisms) the size of the sample may be about 100 ml or more, for example about 250, 500, 750 or 1000 ml or more.

Optional lysis step

In some forms of implementation, after obtaining the sample, the next step in the method of the present invention is the selective lysis of unwanted cells that may be present in the sample, for example blood cells and / or tissue cells. Cells can be lysed to allow microorganisms to separate from other components of the sample. Separation of microorganisms from other components prevents interference during the research phase. If cells of non-microorganisms are not expected to be present in the sample, or they are not expected to interfere at the research stage, there is no need to carry out a lysis step. In one embodiment, the cells to be lysed are non-microorganism cells that are present in the sample, but microorganism cells that may be present in the sample are not lysed. However, in some forms of implementation, selective lysis of certain classes of microorganisms may be desirable and, therefore, it can be carried out in accordance with the methods described in this application and well known in the art. For example, a class of unwanted microorganisms can be subjected to selective lysis, for example, yeast is lysed, while bacteria are not, or vice versa. In another embodiment, the desired microorganisms are lysed to separate a particular subcellular component of the microorganisms, for example cell membranes or organelles. In one embodiment, all non-microorganism cells are lysed. In other forms of implementation, part of the cells of non-microorganisms are lysed, for example, a sufficient number of cells to prevent interference at the stage of research. Cell lysis can be carried out by any method known in the art as effective for selective lysis of cells without lysis or with lysis of microorganisms, including without limitation the addition of a lysis solution, destruction by ultrasound, osmotic shock, chemical treatment and / or a combination thereof.

The lysis solution is such that it has the ability to lyse cells, for example, cells of non-microorganisms (for example, by solubilization of the membranes of eukaryotic cells) and / or cells of microorganisms. In one embodiment, the lysis solution may contain one or more detergents, one or more enzymes, or a combination of one or more detergents and one or more enzymes, and may further include additional agents. In one embodiment, the detergent may be a non-denaturing lytic detergent, such as Triton® X-100, Triton® X-100-R, Triton® X-114, NP-40, Genapol® C-100, Genapol® X-100 , Igepal® CA 630, Arlasolve ™ 200, Brij® 96/97, CHAPS (3 - [(3-cholanidopropyl) dimethylammonium] -1-propanesulfonate), octyl para-D-glucopyranoside, saponin and non-ethylene glycol monododecyl ether (C ₁₂ E ₉ , polydocenol). Optionally, denaturing lytic reagents such as sodium dodecyl sulfate, N-laurylsarcosine, sodium deoxycholate, bile salts, hexadecyltrimethylammonium bromide, SB3-10, SB3-12, amidosulfobetaine-14 and C7BzO can be included. Optionally, solubilizers such as Brij® 98, Brij® 58, Brij® 35, Twin® 80, Twin® 20, Pluronic® L64, Pluronic® P84, non-detergent sulfobetaines (NDSB 201), amphipoles (PMAL-C8) can also be included. and methyl β-cyclodextrin. Typically non-denaturing detergents and solubilizers are used at concentrations above their critical micelle concentration (CMC), while denaturing detergents can be added at concentrations below their CMC. For example, non-denaturing lytic detergents can be used at a concentration of from about 0.010% to about 10%, for example, from about 0.015% to about 1.0%, for example from about 0.05% to about 0.5%, for example, from about 0.10% to about 0.30% (final concentration after dilution with the sample). In another embodiment, detergents comprising a polyoxyethylene detergent may be preferred. The polyoxyethylene detergent may contain a structure of C _12-18 / E _9-10 , where C _12-18 denotes a carbon chain length of from 12 to 18 carbon atoms, and E _9-10 means from 9 to 10 oxyethylene hydrophilic end groups. For example, the polyoxyethylene detergent may be selected from the group consisting of Brij 97, Bnj 96V, Genapol® C-100, Genapol® X-100, non-ethylene glycol monododecyl ether (polydocenol), or a combination thereof.

Enzymes that can be used in lysis solutions include, but are not limited to, enzymes that cleave nucleic acids and other membrane contaminants (e.g., Proteinase XXIII, DNase, Neuraminidase, Polysaccharidase, Glucanex® and Pectinex®). Other additives that can be used include, but are not limited to, reducing agents, such as 2-mercaptoethanol (2-Me) or dithiothreitol (DTT), and stabilizing agents, such as magnesium, pyruvate, and humectants. The lysis solution can be buffered at any pH that is suitable for lysis of the desired cells and depends on many factors, including without limitation the type of sample, cells to be lysed, and the detergent used. In some embodiments, the pH can range from about 2 to about 13, for example from about 6 to about 13, for example from about 8 to about 13, for example, from about 10 to about 13. Buffers with a suitable pH include any buffer, capable of maintaining a pH in the desired range, for example, from about 0.05 M to about 1.0 M CAPS.

In one embodiment, the sample and the lysis solution are mixed and then incubated for a sufficient time so that cell membranes are solubilized, for example, for 1, 2, 3, 4, 5, 10, 15, 20, 25, 30 , 40, 50, or 60 seconds, or about 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 minutes or longer, for example, from about 1 second to about 20 minutes, from about 1 second to about 5 minutes or from about 1 second to about 2 minutes. The incubation time depends on the strength of the lysis solution, for example, on the concentration of detergent and / or enzymes. As a rule, softer lysis buffers will require more time and more dilution of the sample to completely solubilize the cells of non-microorganisms. The strength of the lysis solution can be selected based on microorganisms known or suspected of being in the sample. For microorganisms that are more sensitive to lysis, you can use a mild solution for lysis. Lysis can occur at a temperature of from about 2 ° C to about 45 ° C, for example, from about 15 ° C to about 40 ° C, for example, from about 30 ° C to about 40 ° C. In one embodiment, the lysis solution can be drawn into a syringe, and then the sample can be aspirated into the syringe so that mixing and incubation take place in the syringe.

In some forms of implementation, both lysis conditions (e.g., solution or incubation time) and the steps of separation and / or assay may be sufficient to kill some or all of the microorganisms in the sample. The methods of the present invention are highly versatile and do not require all microorganisms to be alive in order to isolate and identify. In some forms of implementation, some or all of the microorganisms may be dead, where their death occurred before, during and / or after the implementation of the stages of the methods.

Further details and descriptions of the lysis buffers contemplated in the practice of this invention are disclosed in co-filed US Patent Application Serial No. 12 / 589,929, filed October 30, 2009, entitled "Methods for Isolation and Identification of Microorganisms", the contents of which are incorporated herein application by reference.

Separation stage

The next step in the method of the present invention (for example, the step after the sample is lysed if the lysis step is carried out) is the separation step. The separation step can be carried out in order to separate the microorganisms from other components of the sample (for example, non microorganisms or their components) and to concentrate the microorganisms in the sediment, which can be examined for identification and characterization. Separation does not have to be complete, that is, 100% separation is not required. It is only required that the separation of microorganisms from other components of the sample is sufficient to enable the study of microorganisms without significant interference from other components. For example, separation may result in microbial sediment that is at least 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 96, 97, 98, or 99% pure or higher.

In one embodiment, the separation is carried out by a centrifugation step in which a sample (e.g., a lysed sample) is placed on top of a density buffer in a separation container, and the container is centrifuged under conditions that allow isolation of microorganisms (e.g., microorganisms may form a sediment at the bottom and / or on the walls of the container). In accordance with this embodiment, other components of the sample (for example, not microorganisms or their components that may be present in the sample medium) remain on top of the density buffer or inside the upper part of the density buffer. Typically, any known container may be used for the separation step. In one embodiment, the separation container is a separator disclosed in a related patent application, serial No. 12 / 589,969, filed October 30, 2009, entitled "Separation Device for Use in the Separation, Characterization and / or Identification of Microorganisms". This separation step isolates microorganisms from materials in the sample, such as medium, cell detritus and / or other components that could interfere with the study of microorganisms (for example, due to intrinsic fluorescence). In one embodiment, the density buffer also serves to separate living microorganisms from dead microorganisms (which do not pass through the density buffer). In another embodiment, the density buffer does not contain a density gradient either before or after centrifugation. In other words, the separation container is not centrifuged for a sufficient amount of time and / or with sufficient acceleration for the material forming the density buffer to create a density gradient.

The density buffer density is chosen so that microorganisms in the sample pass through this density buffer, while other components of the sample (for example, culture culture medium, cell detritus) remain on top of the density buffer or do not go all the way through the density buffer. The density buffer can also be selected so as to separate living microorganisms (which pass through the density buffer) and dead microorganisms (which do not pass through the density buffer). Suitable densities will depend on the material used in the density buffer and on the sample to be separated. In one embodiment, the density buffer density is in the range of from about 1.025 to about 1.120 g / ml, for example, from about 1.030 to about 1.070 g / ml, from about 1.040 to about 1.060 g / ml, or in any range from about 1.025 to about 1.120 g / ml In another embodiment, the density of the density buffer is about 1.025, 1,030, 1,035, 1,040, 1,045, 1,050, 1,055, 1,060, 1,065, 1,070, 1,075, 1,080, 1,085, 1,090, 1,095, 1,100, 1,105, 1,110, 1,115 or 1,120 g / ml

The density buffer material may be any material that has an appropriate density range for the methods of this invention. In one embodiment, this material is colloidal silica. Colloidal silica may be uncoated (e.g., Ludox® (WR Grace, CT)) or coated, eg, silane (eg, PureSperm® (Nidacon Int′l, Sweden) or Isolate® (Irvine Scientific, Santa Ana, CA) ) or polyvinylpyrrolidone (e.g., Percoll ™, Percoll Plus ™ (Sigma-Aldrich, St. Louis, MO)). In one embodiment, colloidal silica is selected that exhibits the least interference upon spectroscopic examination, for example, material with the lowest intrinsic fluorescence. Colloidal silica can be diluted in any suitable medium to form an appropriate density, for example, in balanced salt solutions, in physiological saline and / or in 0.25 M sucrose. Corresponding densities can be obtained with colloidal silica at a concentration of from about 15% to about 80% v / v, for example from about 20% to about 65% v / v. Another suitable material for the density buffer is an iodinated contrast agent, for example yohexol (Omnipaque ™, NycoPrep ™ or Nycodenz®) and iodixanol (Visipaque ™ or OptiPrep ™). Appropriate densities can be obtained with yogexol or iodixanol at a concentration of from about 10% to about 25% w / v, for example from about 14% to about 18% w / v, for blood culture samples. Sucrose can be used as a density buffer at a concentration of from about 10% to about 30% w / v, for example from about 15% to about 20% w / v, for blood culture samples. Other suitable materials that can be used to obtain a density buffer include low viscosity, high density oils, such as immersion microscope oil (e.g. Type DF; Cargille Labs, NY), mineral oil (e.g. Drakeol®5, Draketex 50, Peneteck®; Penreco Co., PA), silicone oil (polydimethylsiloxane), fluorosilicone oil, silicone gel, metrizoate-Ficoll® (LymphoPrep ™), for example at a concentration of from about 75% to about 100% for blood culture samples, diatrizoate- dextran (PolymorphoPrep ™), e.g. at concentration from about 25% to about 50% for blood culture samples, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyethylene oxide (high molecular weight), Pluronic® F127, Pluronic® F68, mixtures of Pluronic® compounds, polyacrylic acid, crosslinked polyvinyl alcohol, crosslinked polyvinylpyrrolide and methacrylate, pectin, agarose, xanthan, gellan, Phytagel®, sorbitol, Ficoll® (for example, Ficoll® 400 at a concentration of from about 10% to about 15% for blood culture samples), glycerin, dextran (for example, at a concentration of from about 10 % to approx 15% for blood culture samples), glycogen, cesium chloride (for example, at a concentration of from about 15% to about 25% for blood culture samples), perfluorocarbon fluids (e.g. perfluoro-n-octane), hydrofluorocarbon fluids (e.g. Vertrel XF) and the like, which are well known in the art. In one embodiment, the density buffer is selected from one or more of colloidal silica, iodixanol, iohexol, cesium chloride, metrizoate-Ficoll®, diatrizoate-dextran, sucrose, Ficoll® 400 and / or dextran in any combination. The density buffer may also consist of a combination of materials, for example, a combination of colloidal silica and oil. Some combinations of the above compounds may be useful for the separation and reading steps of the present invention, for example, combinations of compounds with various UV damping properties, such as cesium chloride and iohexol.

The volume / height of the density buffer should be sufficient to achieve the separation of microorganisms from other components of the sample. The volume will depend on the size and shape of the separation container. In general, a volume of from about 0.1 to about 5 ml, for example, from about 0.2 to about 1 ml, for example, from about 0.2 ml to about 0.5 ml, can be used. If the separation is carried out on a micro scale, the volume of the density buffer may be from about 1 μl to about 100 μl, for example from about 5 μl to about 50 μl. The volume of the sample, deposited or layered on top of the density buffer, should be sufficient to provide a sufficient number of microorganisms to obtain a precipitate suitable for research. You can usually use any volume that goes into the container. For example, a volume of from about 0.1 ml to about 5 ml, for example, from about 0.2 ml to about 1 ml, for example, from about 0.2 ml to about 0.5 ml, can be used. If the separation is carried out on a micro scale, the sample volume can be from about 1 μl to about 100 μl, for example, from about 5 μl to about 50 μl. The available space in the sample container will depend on the size and shape of the container. In some embodiments, an intermediate layer (liquid or solid) can be placed on top of the density buffer before applying or overlaying the sample on top to prevent any mixing of the density buffer and the sample. In one embodiment, the intermediate layer may be polyethylene granules. In another embodiment, a small air bubble can be positioned between the density buffer and the sample to prevent mixing. In a further embodiment, the density buffer can be layered on top of a high density material (e.g., perfluorocarbon liquid) so that microorganisms pass through the density buffer during separation and are collected at the interface between the density buffer and high density material.

In one embodiment of the invention, the separation container is centrifuged in an oscillating rotor, so that microorganisms form a precipitate directly at the bottom of the container. The container is centrifuged at sufficient acceleration and for a sufficient time to separate microorganisms (for example, a precipitate formed) from other components of the sample. The centrifugation acceleration can be from about 1000 × g to about 20,000 × g, for example, from about 2500 × g to about 15000 × g, for example from about 7500 × g to about 12,500 × g, etc. The centrifugation time may be from about 30 seconds to about 30 minutes, for example, from about 1 minute to about 15 minutes, for example from about 1 minute to about 5 minutes. Centrifugation can be carried out at a temperature of from about 2 ° C to about 45 ° C, for example, from about 15 ° C to about 40 ° C, for example, from about 20 ° C to about 30 ° C. In one embodiment, the separation container comprises a lid, and the lid is applied to the container to form an airtight seal before centrifugation. The presence of a cap reduces the risk of handling microorganisms that are or may be infectious and / or dangerous, as well as the risk of contamination of the sample. One of the advantages of the methods of the invention is the ability to carry out one or more of the steps of these methods (e.g., lysis, separation, assay, and / or identification) with microorganisms in an airtight container (e.g., an airtight container). These methods, including the use of automated systems, avoid the health and safety risks associated with the handling of highly virulent microorganisms, which occurs when microorganisms are isolated from samples for direct testing. In one embodiment, the container is not centrifuged for a sufficient time and / or is not subjected to sufficient acceleration so that a density gradient forms inside the density buffer. The present invention does not include ultracentrifugation of samples, for example, centrifugation at accelerations higher than about 100,000 × g. In addition, the present invention does not include isopycnic (equilibrium) sedimentation or banding.

The separation container may be any container of sufficient volume to hold the density buffer and sample. As noted in this application, the separator disclosed in US Patent Application Serial No. 12/589969, filed October 30, 2009, entitled "Separation Device for Use in the Separation, Characterization and / or Identification of Microorganisms", can be used in practice. of the present invention. In one embodiment, the container is adapted or may be adapted to a centrifugal rotor. The volume of the container may be from about 0.1 ml to about 25 ml, for example from about 1 ml to about 10 ml, for example, from about 2 ml to about 8 ml. If the separation is carried out on a microscale, the volume of the container may be from about 2 μl to about 100 μl, for example from about 5 μl to about 50 μl. In one embodiment, the container has a wide inner diameter in the upper part to hold the sample and the main part of the density buffer and a narrower internal diameter in the lower part where the microorganism sediment is collected. The narrow portion may have an inner diameter of from about 0.04 (1.02 mm) to about 0.12 (3.05 mm) inches, for example, from about 0.06 (1.52) to about 0.10 (2, 54 mm) inches, e.g., approximately 0.08 (2.03 mm) inches. The wide part may have an inner diameter from about 0.32 (8.13 mm) to about 0.40 (10.16 mm) inches, for example from about 0.34 (8.64 mm) to about 0.38 (9, 65 mm) inches, for example, approximately 0.36 (9.14 mm) inches. For micro-scale separations, the inner diameters can be even smaller. For example, the inner diameter of the narrow portion may be from about 0.001 (0.03 mm) to about 0.04 (1.02 mm) inches, for example, from about 0.002 (0.05 mm) to about 0.01 (0.254 mm) inches. The conical part of the inner diameter can connect the upper and lower parts. The conical portion may have an angle of from about 20 to about 70 degrees, for example from about 30 to about 60 degrees. In one embodiment, the lower narrow portion is less than half of the total height of the container, for example less than about 40%, 30%, 20%, or 10% of the total height of the container. The container may have a closure device that is attached or may be threaded to attach the closure device (eg, cap) so that the container can be hermetically sealed during centrifugation. In some forms of implementation, the container is designed so that a sample or sediment of microorganisms can be easily isolated, or otherwise obtained or removed from the container after separation, either manually or automatically (so that laboratory assistants are not exposed to the contents of the container). For example, the container may contain a detachable part or a detachable part that contains sediment and which can be separated from the rest of the container. In another embodiment, the container comprises means for accessing the sediment after separation, such as one or more openings or one or more permeable surfaces for inserting a syringe or other dispenser or for drawing out the sediment. In one embodiment, the container may be a tube, for example a centrifuge tube. In another embodiment, the container may be a chip or a board. In one embodiment, the container is a freestanding container, that is, a device for separating one sample. In other embodiments, the container is part of a device that includes two or more than two separation containers, so that multiple samples can be separated at the same time. In one embodiment, the device includes 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30, 36, 42, 48, 60, 72, 84, 96 or more separation containers.

The container may comprise an optical window through which research can be carried out. The optical window may be located on the bottom, top and / or on the walls of the container. This window may consist of any material with an oscillatory structure that can be distinguished from the spectra of a microorganism. Other methods of discrimination, such as confocal Raman spectroscopy, can be used to record the vibrational spectra of a microorganism when the spectra of the window material are deflected; this method is well known to those skilled in the art. An additional method is spatial displacement Raman spectroscopy, in which the exciting fiber deviates from emission along the window (Rayleigh and Raman spectra). This method is also known to those skilled in the art as a means of discriminating between window material and the amount to be measured below the window. In order to provide additional spectroscopic methods for studying the sediment of microorganisms, the window should also consist of any material that is transparent to light (for example, at least part of the near infrared (NIR; 700 nm - 1400 nm), ultraviolet (UV; 190 nm - 400 nm ) and / or visible (VID; 400 nm - 700 nm) light spectrum). In one embodiment, the optical window is thin enough to allow spectroscopic examination, which will depend on the material of the window and on the method used for the study. In another embodiment, it is as subtle as possible in order to reduce interference in spectroscopic examination. For example, a window may have a thickness of less than about 0.20 (5.08 mm) inches, for example, less than about 0.15 (3.8 mm), 0.10 (2.54 mm), or 0.05 (1 , 27 mm) inches.

In another embodiment, the separation is carried out by a filtration step in which a sample (eg, a lysed sample) is placed in a device equipped with a selective filter or a set of filters with pore sizes that trap microorganisms. Trapped microorganisms can be washed by carefully passing a suitable buffer through the filter. The washed microorganisms can then be examined directly on the filter and / or isolated for testing by direct sampling from the surface of the filter or by backwashing the filter with a suitable aqueous buffer.

Research stage

Once the microorganisms are separated, isolated and / or precipitated, the separated sample, isolated sample or pellet can be examined to identify and / or characterize the microorganisms in the sample or pellet. In one embodiment, the study is conducted in a non-invasive manner, that is, the sediment is examined while it remains in the separation container. In another embodiment, the separation container remains airtight throughout the study. The ability to identify microorganisms in a non-invasive way, optionally in combination with keeping the container sealed throughout the separation and identification / characterization process and the full or partial automation of the method, avoids the constant handling of infected and / or infectious samples and significantly increases the safety of the whole process. In addition, the ability to identify microorganisms by direct examination without additional treatment of the sediment (for example, resuspension, plating and growing colonies) significantly increases the speed with which identification can be carried out. In one embodiment, the precipitate is isolated and / or resuspended and optionally removed from the separation container prior to testing. In another embodiment, the precipitate is isolated and / or resuspended after an in situ study, and then an additional study is performed. For example, techniques such as latex agglutination reactions or automated phenotypic identification tests that can be applied to isolated microorganisms but not to microorganism sediment can be performed on isolated and / or resuspended microorganisms.

In some embodiments, an isolated sample or precipitate can be examined spectroscopically. Spectroscopy can be used to analyze one or more than one intrinsic property of microorganisms, for example, a property present inside a microorganism in the absence of additional agents, such as dyes, contrast agents, binding agents, etc. In other forms of implementation, spectroscopy can be used to analyze one or more external properties of microorganisms, for example properties that can only be detected using additional agents. The study can be carried out using, for example, infrared spectroscopy, Raman spectroscopy, including surface enhanced Raman spectroscopy (SERS), spatial displacement Raman spectroscopy (SORS), transmission Raman spectroscopy and / or resonant Raman spectroscopy. To enhance Raman (SERS) signals, microorganisms can be coated with gold and / or silver nanoparticles before centrifugation, and / or the internal optical surface can be precoated with metal colloids of a certain size and shape (Efrima et al, J. Phys. Chem. B. ( Letter) 102: 5947 (1998) for SERS). In another embodiment, the nanoparticles are present in the density buffer prior to centrifugation and bind to microorganisms when the microorganisms pass through the density buffer. In one embodiment, an isolated sample or precipitate is examined when it remains in a separation container. The container can be examined through an optical window in this container. The optical window may be at the bottom and / or on any wall or walls and / or at the top of the container. In one embodiment, the separation container is matched or can be matched to the holder in the spectrometer in a suitable position for examination. Spectroscopic examination can be carried out by any method known to specialists in this field of technology, which should be effective for determining and / or identification of one or more than one of the internal or external properties of microorganisms. In another embodiment, as described herein, an isolated sample or precipitate can be removed for research (for example, an isolated sample or precipitate can be removed and prepared for research using mass spectrometry, as is well known in the art). In the following embodiments, an isolated sample or precipitate can be investigated using more than one method. For example, an isolated sample or precipitate can be investigated using fluorescence spectroscopy and Raman spectroscopy. In accordance with this form of implementation, these stages of the study can be carried out sequentially or simultaneously.

The source of excitation of the sample can be selected from any number of suitable light sources, as is well known to specialists in this field of technology. Any part of the electromagnetic spectrum that provides applicable data may be used. Light sources capable of emitting in the ultraviolet, visible and / or near infrared spectrum, as well as in other parts of the electromagnetic spectrum, can be used and known to specialists in this field of technology. Since the generation of Raman spectra is usually an inefficient process (for example, 1 Raman photon generated for every 1 million random photons), Raman spectroscopy requires light sources with a large flux of photons. Since the invention of the laser in 1960 (Maiman, Nature), Raman systems have used a laser light source to obtain Raman spectra. Laser light passes through a highly selective (narrow-band notch filter), which allows a narrow band of laser emission wavelengths to pass through the filter, while blocking other artifacts generated by the laser (for example, amplified spontaneous emission, fluorescence, plasma lines, etc. .).

Light from the laser is directed into the sample using a variety of optical systems that can be created using reversing lens systems, optical fibers, or combinations thereof. Laser light is focused on the sample using lenses (such as a microscope lens), so that a small spot of concentrated optical energy is obtained on the sample.

Raman backscattered light and backscattered exciting light are collected and collimated with the same microscope objective. The scattered light passes through an optical filter that separates the Raman scattered light from the exciting light. Then, Raman scattered light is distributed, using lenses and / or a fiber optic system, to a spectrometer that disperses the Raman scattered light in such a way that it collides with the CCD array of detectors.

The spatial dispersion of Raman scattered light generates spectra (e.g., scattered wavelength versus intensity) that can be stored and compared with reference spectra for characterization.

Emission from a sample can be measured using any suitable spectral separation means, most preferably using a spectrometer. The spectrometer may be a scanning monochromator that determines specific emission wavelengths, where the output of the monochromator is determined by a photomultiplier, and / or the spectrometer may be configured as a visualization spectrograph, where the output is determined by an array of imaging detectors, such as a charge-coupled detector array (CCD) matrix). In one embodiment, the discriminator makes it possible to observe the fluorescence and / or scattering signal using photodetection tools (such as a photomultiplier tube, avalanche photodiode, CCD detector array and / or charge coupled detector electron multiplier matrix (EULS)).

In accordance with the invention, control measurements are taken from known microorganisms, which thus makes it possible to correlate the measured test data with the characteristics of the microorganisms of interest, using various mathematical methods known to those skilled in the art. For example, data from samples can be compared with a baseline or with control measurements using software systems known to those skilled in the art. More specifically, data can be analyzed using a variety of multivariate analysis methods, such as, for example, General Discrimination Analysis (GDA), Partial Least Squares Discrimination Analysis (PLSDA), Partial Least Squares Regression Analysis, Principal Component Analysis (PCA), Parallel Factor Analysis (PARAFAC ), neural network analysis (NNA) and / or reference vector method (SVM). These methods can be used to classify unknown microorganisms of interest into relevant groups based on existing nomenclature and / or naturally occurring groups based on metabolism, pathogenicity and / or virulence of an organism, when developing a monitoring system, determining and / or characteristics of an organism, as described above.

In yet another embodiment, non-spectroscopic measurements by the detection system, such as periods of detection time and growth rate, can be used to facilitate characterization and / or identification of microorganisms from an isolated sample or sediment. In addition, measurements taken from a photographic image of the bottom of the separator can provide valuable information on the identity of the isolate, such as size, shape, color and density of the precipitate.

In some embodiments, the characterization and / or identification of microorganisms in an isolated sample or pellet optionally includes identification of the exact species. The characteristic covers both a broad categorization or classification of biological particles and the actual identification of a particular species. Classification of a microorganism from an isolated sample or sediment may include determination of the phenotypic and / or morphological characteristics of the microorganism. For example, the characterization of biological particles can be performed based on observed differences, such as composition, shape, size, clustering and / or metabolism. In some forms of implementation, the classification of biological particles of interest may not require prior knowledge of the characteristics of a given biological particle, but only requires appropriate correlations with empirical measurements, which thus makes this method more versatile and easily adaptable than methods based on specific binding events or metabolic reactions . As used in this application, "identification" means determining which family, genus, species and / or strain a previously unknown microorganism belongs to, for example, identifying a previously unknown microorganism at the family, genus, species and / or strain level.

In some cases, the characteristic encompasses classification models that provide sufficiently useful information for the action to be taken. As used herein, preferred classification models include grouping into one or more than one of the following: (1) Gram groups; (2) Gram clinical groups; (3) therapeutic groups; and (4) functional groups.

(1) Gram groups: Within the Gram group classification, microorganisms can be placed in one of three broad classification categories based on their Gram staining reaction and overall size, where these groups are selected from one or more than one of the following: ( a) gram-positive microorganisms that are stained in dark blue when stained by Gram; (b) gram-negative microorganisms that are colored red when stained by Gram; and (c) yeast cells, which are stained dark blue when stained according to Gram, but are very large round cells that differ from bacteria in their morphological characteristics and size.

(2) Gram Clinical Groups: Gram groups can be further divided into several subcategories representing differing morphological characters. These subcategories include all relevant clinical information reported by a qualified clinical laboratory technician, and thus provide a higher level of identification than a positive or negative Gram response. This particular classification is very useful because it eliminates problems based on the quality of the Gram strain and / or on the skill level of the lab technician examining the smear by providing equivalent clinically relevant information to the automated system. More specifically, subcategories of microorganisms based on this classification model can be selected from one or more than one of the following: (a) cocci, which are small round cells; (b) diplococci, which are two small rounded cells connected together; (c) sticks that are rectangular; and (d) bacilli, which are rod-shaped. Examples of these subcategories that may be supported by additional morphological information include: (i) gram-positive cocci; (ii) gram-positive cocci in chains; (iii) gram-positive cocci in clusters (ie clusters in the form of a "bunch of grapes"); (iv) gram-positive diplococci; (v) gram-positive sticks; (vi) gram-positive rods with endospores; (vii) gram-negative rods; (viii) gram-negative coccobacilli; (ix) gram-negative diplococci; (x) yeast; and (xi) mycelial fungi.

(3) Therapeutic groups: therapeutic groups include many types of microorganisms that, when isolated from specific types of samples, are treated with the same class of antibiotics or a mixture of antibiotics (for example, as described in the Sanford Guide to Antimicrobial Therapy 2008). In many cases, species-specific identity is not required by the physician to ensure the transition from initial empirical therapy to more targeted therapy, since more than one species can be treated with the same antibiotic (s) of choice. This level of classification correctly places these microorganisms of the “same treatment” into single therapeutic categories. Examples of this level of performance include the ability to distinguish highly resistant Enterobacteriacae (EB) species from sensitive EB species (Enterobacter spp. From E. coli) or fluconazole resistant Candida species (C. glabrata and C. kruzei) from sensitive Candida species (C. albicans and C. parapsilosis), etc.

(4) Functional groups: According to the invention, microorganisms can also be placed in several groups based on a combination of metabolic, virulent and / or phenotypic characteristics. Non-enzymatic organisms can be clearly distinguished from enzymatic ones. In addition, the types of microorganisms that produce hemolysins can be grouped separately from non-hemolytic species. In some cases, these groups represent broader categories than the genus level (for example, E. coli bacteria, gram-negative non-enzymatic rods), in some cases at the genus level (for example, Enterococcus, Candida), and in some cases closer to species-level discrimination (e.g. coagulase-negative staphylococci, alpha-hemolytic streptococci, beta-hemolytic streptococci, coagulase-positive staphylococci, i.e. S. aureus).

In addition to measuring the intrinsic properties of microorganisms for identification purposes, the methods of the present invention may further include the use of additional identifiers to facilitate the separation and / or identification process. Agents that bind to specific microorganisms, such as affinity ligands, can be used to separate microorganisms, to identify the class or type of microorganism (e.g., by binding to a unique surface protein or receptor), and / or to identify the characteristics of the microorganism (e.g. antibiotic resistance ) Useful identifiers include, but are not limited to, monoclonal and polyclonal antibodies and fragments thereof (e.g., anti-Ep for identification of S. aureus), nucleic acid probes, antibiotics (e.g., penicillin, vancomycin, polymyxin B), aptamers, peptide mimetics, binding phage proteins origin, lectins, biomarkers of innate host immunity (acute phase proteins, LPS-binding protein, CD 14, mannose-binding lectin, Toll-like receptors), immune defense proteins (e.g. defensins, cathelicidins, proteogrins, magainins), b acteriocins (e.g. lantibiotics such as nisin, mercacidin, epidermis, gallidermin and plantaricin C, and class II peptides), bacteriophages and dyes selective for nucleic acids, lipids, carbohydrates, polysaccharides, capsules / mucus or proteins, or any combination thereof . If the agent itself does not give a detectable Raman signal, this agent can be labeled to give a detectable signal, for example, by conjugating an agent with a Raman active indicator, such as dimethylaminoazobenzene (DAB) and 4.4 ″ -dipyridyl (DPY) (see for example, US patents No. 5376556 and 7518721). The agent can be added to microorganisms at any stage in the methods of the invention, for example, when a sample is obtained, during lysis and / or during separation. In some embodiments, the presence of an agent in the precipitate can be determined during the study of the precipitate. As should be readily understood by those skilled in the art, the sensitivity of a particular microorganism to a compound that affects its physical condition or metabolism, such as an antibiotic, can be easily detected by adding this compound to a sample, lysis buffer, density buffer, or any their mixture.

In one aspect of the invention, the method may further include the step of isolating the sediment of microorganisms and conducting additional tests. In one embodiment, the precipitate can be isolated by aspirating the sample medium and the density buffer. In another embodiment, the pellet can be isolated by inserting a syringe into the container and aspirating the pellet, while the sample medium and density buffer remain intact. Then the precipitate can be resuspended in a suitable medium, for example, in physiological saline. Once the microorganisms are resuspended, they can be subjected to any additional tests that are desirable, as should be known to specialists in this field of technology, and as described above. In particular, any test that requires clean samples of microorganisms with resuspended microorganisms can be performed. In some forms of implementation, additional identification tests may be performed. Examples of identification tests include Vitek® 2, amplified and non-amplified nucleic acid (NAT) tests, chromogenic assays and latex agglutination reactions, immunological assays (e.g. using labeled antibodies and / or other ligands), mass spectrometry (e.g. MALDI- TOF mass spectrometry) and / or other optical methods such as infrared spectroscopy (FTIR) or Raman spectroscopy. Additional characterization tests, such as antibiotic and / or other drug resistance, can also be performed. An additional characteristic may be part of the test that was started during the initial stages of separation and identification of the method. For example, the determination of S. aureus resistant to methicillin can be started by adding penicillin labeled with a Raman indicator to the sample before microorganisms are separated. Once the precipitate is isolated and resuspended, the level of bound penicillin can be determined.

In one aspect of the invention, some or all of the steps of the method may be automated. Automation of the stages of the methods makes it possible to more effectively test a larger number of samples and reduces the risk of human errors when handling samples that may contain harmful and / or infectious microorganisms.

In some embodiments, these methods can also be used to determine the presence of microorganisms in a sample. In these forms of implementation, the methods include the steps of:

(a) obtaining a sample;

(b) optionally lysing the cells in this sample to obtain a lysed sample; and

(c) the separation of microorganisms and other components of the sample with the formation of sediment of microorganisms;

where the presence of sediment indicates that microorganisms are present in the sample. In one embodiment, the precipitate is determined with the naked eye. In other forms of implementation, the precipitate is determined by examination, for example, spectroscopic.

In some forms of implementation, the determination methods can be used to monitor samples for infection by microorganisms, for example, foods, pharmaceuticals, drinking water, etc. In one form of implementation, these methods can be carried out with repetition for continuous monitoring of infection, for example, once a month, once a week, once a day, once an hour, or according to any other periodicity scheme. In another embodiment, the samples can be tested as needed, for example, when infection is suspected. In the following embodiments, the determination methods can be used to see the presence of microorganisms in clinical samples, for example, in blood cultures. For example, a sample can be taken from a blood culture at specific points in time and a determination method can be carried out on a sample to determine if the blood culture is positive. In one embodiment, a sample can be taken at a specified point in time after inoculation of the culture, for example, 24 hours after inoculation, to determine if this blood culture is positive. In another embodiment, samples can be taken from the blood culture regularly, for example, every 12, 6, 4, or 2 hours, or every 60, 50, 40, 30, 20, 15, 10, or 5 minutes to identify positive blood cultures within a short period of time. as detectably positive. In some forms of implementation of the determination methods, the identification step may be optionally followed by the identification methods described in this application.

In one aspect of the invention, some or all of the steps of the method can be automated. Automation of the stages of the methods makes it possible to more effectively test a greater number of samples and reduces the risk of human errors when handling samples that may contain harmful and / or infectious microorganisms. Of great importance, however, is that automation can produce critical results at any time of the day or night without delay. Several studies have shown that faster identification of organisms that cause sepsis correlates with better patient care, a shorter hospital stay and lower overall costs.

Further details and a description of a method for characterizing and / or identifying microorganisms in accordance with the present invention are disclosed in co-filed US Patent Applications Serial Nos. 12/589952 and 12/589936, both filed October 30, 2009, entitled "Method for Separation, Characterization and / or Identification of Microorganisms using Spectroscopy "and" Method for Separation, Characterization and / or Identification of Microorganisms using Mass Spectrometry ", respectively, the contents of which are incorporated herein by reference.

The present invention is described in more detail in the following examples, which are provided by way of illustration and are in no way intended to limit the invention. Use standard methods well known in the art, or methods specifically described below.

EXAMPLES

Example 1. The method of lysis-centrifugation to identify microorganisms from hemocultures using Raman spectroscopy

Microorganisms were plated at low inoculum into BacT / ALERT® SA vials containing 10 ml of human blood. Samples of the culture medium of the hemoculture were taken from the vials within a few minutes after positive labeling with the BacT / ALERT® 3D microorganism detection system. Samples of the culture medium were processed to separate microorganisms from blood and medium components that could interfere with subsequent analysis, as described below:

4.0 ml of culture medium from fresh positive blood cultures was combined with 2.0 ml of lysis buffer (0.45% Brij® 97 in 0.3 M CAPS, pH 11.7), vortexed for 5 seconds, and then incubated in a 37 ° C water bath for 90 seconds. After incubation, 0.95 ml of the lysate was layered on top of 0.5 ml of density buffer (14% w / v yohexol, 0.005% Pluronic F-108 in 10 mM HEPES, pH 7.4) in each of four 1.5 ml conical centrifuge tubes. Then, all four tubes were centrifuged for 2 minutes at 10,000 g at 25 ° C until sedimentation (sedimentation) of microorganisms through a density buffer. Lysed blood and medium remained above the density buffer.

After the centrifugation cycle was completed, the supernatant was removed and the sedimented (precipitated) microorganisms in each tube resuspended 10 μl of distilled water. Resuspended microorganisms from all 4 tubes were combined in a clean tube and gently mixed. Then, the volume of each treated sample was adjusted so that the optical density at 660 nm (A ₆₆₀ ) of the final suspension was 20 / cm. Treated samples of lidos were stored at 2-8 ° C during the same day of testing, or were aliquoted and frozen at -70 ° C for testing on the next day.

Example 2. Analysis of samples of microorganisms processed from positive blood cultures by lysis-centrifugation using Raman spectroscopy

Samples processed in accordance with the procedure in example 1 were quickly thawed at 37 ° C (if previously frozen), gently mixed. Part of the sample was kept undiluted, and the rest of the sample was diluted to 1: 2 in distilled water. One microliter of each diluted and undiluted sample was applied to the first surface of a gold-coated microscope slide and allowed to dry under ambient conditions.

After drying, 25 spectra in a 5 × 5 lattice scheme were recorded for each of the dried samples using a Model R × N1 Raman microscope (Kaiser Optical Systems Inc., Michigan) at a light wavelength of 785 nm. The microscope was equipped with a 40X lens, the laser power was set to 400 MW, and each of the 25 individual spectra was recorded with a 5-second accumulation time.

After removal, the spectra were preliminarily processed to subtract darkness, remove the cosmic ray artifact, spectral compression, subtract the base level, normalize and remove sharply deviating values in preparation for multivariate statistical analysis and its implementation.

Representative Raman spectra of selected microorganisms isolated and processed from positive blood cultures are shown in FIG. 1 and 2. In FIG. 1 shows the spectra of four types of microorganisms; four isolates of C. albicans; six isolates of P. aeruginosa; thirteen isolates of E. coli; and thirteen isolates of S. aureus. Spectra from each species were averaged for clarity of illustration.

Corresponding differences in all spectra of various species are easily obvious for these organisms. This shows that potentially masking blood and culture media are sufficiently removed to obtain characteristic spectra for microorganisms after treatment.

In FIG. 2 shows 13 individual Raman spectra of S. aureus isolates, which were shown averaged in FIG. 1. These thirteen spectra show the correspondence of the Raman spectrum to this microorganism for all different clinical isolates, even grown in different blood cultures from various blood donors.

Example 3. Non-invasive analysis of samples of microorganisms processed from positive blood cultures by lysis-centrifugation using Raman spectroscopy

Microorganisms were plated at low inoculum into BacT / ALERT® SA vials containing 10 ml of human blood. Samples of the culture medium of the hemoculture were taken from the vials within a few minutes after positive labeling with the BacT / ALERT® 3D microorganism detection system. Samples were processed as described below:

1. A 2.0 ml sample of positive culture medium was mixed with 1.0 ml of selective lysis buffer (0.45% w / v Brij® 97 + 0.3 M CAPS, pH 11.7), then placed in water bath at 37 ° C for 1 minute.

2. A 1.0 ml lysate sample was layered on top of 0.5 ml of density buffer (24% w / v cesium chloride in 10 mM HEPP pH 7.4 + 0.005% Pluronic F-108) contained in a custom optical separation tube. A polypropylene ball was present on the surface of the density buffer to facilitate application without disturbing the aqueous phases.

3. The optical separation tube was sealed with a screw cap and centrifuged for 2 minutes at 10,000 rpm (Eppendorf® 5417R microcentrifuge equipped with an A-8-11 oscillating rotor, see FIG. 4).

4. The hermetically sealed tube was transferred to a custom adapter, which facilitated the study of microorganism sediment in the base of the tube using a Model R × N1 Raman microscope (Kaiser Optical Systems Inc., Michigan) at a light wavelength of 785 nm. Spectra of empty separation tubes were also recorded to establish the baseline of the Raman spectrum of plastics.

In FIG. Figure 3 shows Raman spectra taken through a plastic separation tube, both with and without a sediment of microorganisms. In this mode, Raman bands from the plastic itself prevail in the spectra; however, bands unique to microorganisms are visible in the spectrum of microorganism sediment only at wave numbers of about 1227 / cm, 1583 / cm and 1660 / cm. Other bands of the microorganism are also present, but masked by stronger bands of plastic on this scale.

In FIG. Figure 4 shows the Raman spectra of three microorganisms after removing the background by subtracting the spectrum of an empty plastic separation tube. Although this background subtraction is not 100% effective, the spectral bands of microorganisms are clearly visible. Other removal system geometries, such as spatial offset removal or transmission removal, are likely to further enhance background compensation (see, for example, published U.S. Patent Application Nos. 2008/0129992 and 2009/0244533).

The above examples are illustrative of the present invention and should not be construed as limiting it. The invention is defined by the claims below, where equivalents of the claims are to be included therein. All publications, patent applications, patents, patent publications, and any other references cited in this application are incorporated in their entirety by reference to information relevant to the proposal and / or paragraph in which the reference is made.

Claims (13)

1. A method for identifying a microorganism from a test sample of a blood culture, including:
(a) obtaining a test sample known to contain microorganisms;
(b) selectively lysing and dissolving the non-microorganism cells of the test sample using a lyse solution to obtain a sample lysate, wherein said lyse solution has a pH of from about 8 to about 13;
(c) layering said sample lysate on a density buffer, where said density buffer has a uniform density of from about 1.025 g / ml to about 1.120 g / ml, in a sealed container and further centrifuging the container to separate and isolate said microorganisms from other components in the lysate a sample where microorganisms passing through the density buffer form a precipitate at the bottom of the specified container;
(d) examining said precipitate using one or more than one Raman spectroscopy method to obtain spectroscopic measurements of a given microorganism, wherein said Raman spectroscopy studies are carried out with a microorganism sediment remaining at the bottom of the container, and
(e) identifying a given microorganism in said sediment by comparing spectroscopic measurements with spectroscopic measurements of known microorganisms or the predicted spectroscopic properties of known microorganisms, where microorganisms are identified at the genus or species level. 2. The method according to claim 1, where the stage of the study (d) is non-invasive. 3. The method according to claim 1, where the Raman spectroscopy method is selected from the group consisting of Raman spectroscopy, confocal Raman spectroscopy, surface enhanced Raman spectroscopy, spatial offset Raman spectroscopy, resonance Raman spectroscopy, transmission Raman spectroscopy, and any combination thereof. 4. The method according to claim 1, where the stage of selective lysis (b) is carried out using a lysis solution containing one or more than one detergent. 5. The method according to claim 4, where one or more than one detergent is selected from the group consisting of Triton® X-100, Triton® X-100-R, Triton® X-114, NP-40, Genapol® C-100 , Genapol® X-100, Igepal® CA 630, Arlasolve ™ 200, Brij® 96/97, CHAPS, octyl-D-glucopyranoside, saponin, non-ethylene glycol monododecyl ether (C ₁₂ E ₉ , polydocenol), sodium dodecyl sulfate, N-lauryl sarcos , sodium deoxycholate, bile salts, hexadecyltrimethylammonium bromide, SB3-10, SB3-12, amidosulfobetaine-14, C ₇ BzO, Brij® 98, Brij® 58, Brij® 35, Tween® 80, Tween® 20, Pluronic® L64, Pluronic® P84, non-detergent sulfobetaines (NDSB 201), amphipoles (PMAL-C8) and methyl-β-cy clodextrin. 6. The method according to claim 4, where the specified detergent is a polyoxyethylene detergent comprising the structure C _12-18 / E _9-10 . 7. The method according to claim 6, where the specified polyoxyethylene detergent is selected from the group consisting of Brij® 97, Brij® 96V, Genapol® C-100, Genapol® X-100 and polydocenol. 8. The method of claim 4, wherein the lysis solution further comprises one or more enzymes, which comprises a mixture of one or more proteinases and one or more than one nuclease. 9. The method according to claim 4, where the solution for lysis contains one or more than one buffering agent. 10. The method according to claim 1, where the specified density buffer is selected from the group consisting of colloidal silica, iodinated contrast agents, sucrose, immersion oil for a microscope, mineral oil, silicone oil, fluorosilicon oil, silicone gel, metrizoic-ficoll®, diatrizoate -dextran, carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyethylene oxide (high molecular weight), Pluronic® F127, Pluronic® F68, polyacrylic acid, crosslinked polyvinyl alcohol, crosslinked polyvinylpyrrolidine, methyl e copolymer PEG and methacrylate, pectin, agarose, xanthan, gellan, Phytagel®, sorbitol, ficoll®, glycerol, dextran, glycogen, cesium chloride, perfluorocarbon fluids and / or hydrofluorocarbon fluids and combinations thereof. 11. The method according to claim 1, where the test sample is a culture sample, of which it is known that it contains microorganisms. 12. The method according to claim 1, where the specified test sample is a sample of blood culture. 13. The method according to claim 1, where the specified density buffer contains cesium chloride or iohexol.

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